Note: I’ve

split my answer for this question up into two posts.

a) What is

the basis of the Fermi Paradox and explain the close connection it has to the

Drake Equation?

13.6 billion years old 1. 100 000 light years in diameter 2. Hundreds

of billions of stars.

The Milky Way is a pretty big place.

Given that the Earth is relatively young (only 4.54 billion years old 3) and

we have intelligent life, shouldn’t the night sky should be teeming with other lifeforms

from older, more advanced civilizations?

Where are they all?

This contradiction between the idea that there should be many intelligent

extraterrestrials and the lack of evidence for them is what forms the basis of the

Fermi Paradox 4.

It suggests that the reason why we haven’t come into contact with

extraterrestrials is either because 4, 5 & 6:

1.

There are actually none (or very few) exist in our galaxy. In

other words, the answer to the Drake equation is 0 (or an extremely small

number).

2.

There are factors that affect the possibility of communicating with

extraterrestrials which we have not taken into account in the Drake equation.

For those who are not yet aware of the Drake equation, it the

theoretical formula in Image 1 that estimates the number of communicative extraterrestrial

civilisations there are in the Milky Way galaxy 6. To understand what each term

in the Drake equation represents in more detail, and what their numerical

values might be, I strongly advise that everyone reads Ziyi’s answer to another

question that someone else posted before continuing. (https://moodle.telt.unsw.edu.au/mod/forum/discuss.php?d=643404).

Now, the Fermi Paradox implies that instead of having

to hypothesise inputs for the Drake equation, one can just look at the empirical

evidence that supports the existence of intelligent extraterrestrials 8. If

there were any intelligent technological civilizations in the Milky Way, they should’ve

been capable of colonize a large majority of the entire Milky Way by now. According

to the mathematicians Duncan Forgan and Arwen Nicholson, even at the modest

velocity of 10% the speed of light, the whole galaxy should be accessible

within 10 million years 9.

However, we are yet to find any kind proof that

suggests communicative aliens exist. Thus, why the Fermi Paradox implies that either

none exist (and the Drake equation’s answer is 0) or there is some unknown

factor that we haven’t taken into account (missing variable from Drake

equation).